WASHINGTON — The Republican Party should have done more to shut down the birther movement that Donald Trump led, one GOP senator said Sunday.

“I wish that we, as a party, would have stood up, for example, when the birtherism thing was going along,” Sen. Jeff Flake (R-Ariz.) told NBC’s “Meet the Press.” “A lot of people did stand up but not enough.”

Long before he was a presidential candidate, Trump led an effort to discredit President Barack Obama by questioning whether he was a US citizen. Obama was born in Hawaii.

While many Republicans stood up to Trump, the party leadership should have condemned more of the “ugly conspiracy theories,” Flake said.

Flake is up for re-election in 2018 and released a new book about reclaiming conservatism in the era of Trump and the “sugar high of populism.”

The party also needed to shut down the popular Trump rally chant of “Lock her up!” against Hillary Clinton​, he said​.

“We shouldn’t be the party for jailing your political opponents,” Flake said. “Anybody at those rallies ought to stand up and say, ‘That’s inappropriate. We shouldn’t be doing that.’”